Book/Dissertation / PhD Thesis

FZJ-2020-01447

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Leistungssteigerung metallgestützter Festelektrolyt-Brennstoffzellen (MSCs) durch gezielte Optimierungen des Anoden / Elektrolytverbunds

Bischof, C. (Corresponding author)FZJ*

2020
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-455-3

Please use a persistent id in citations: http://hdl.handle.net/2128/24815

Abstract: This work addressed the perfomance increase of metal-supported solid oxide fuel cells (MSCs) by optimization of the anode/electrolyte interface. Properties of the anode are strongly influenced by process parameters of the used screen printing process, a powder-based process. In comparison, properties of the electrolyte are influenced by process parameters of a specific physical vapor deposition (PVD) method. In this work, both processes were adapted to increase cell performance by improving cell design, cell layer thicknesses and microstructures. The goal of this work was the increase of the electrochemically active surface and the decrease of polarization resistances of the anode functional layer and ohmic resistances of the electrolyte. In a first step, cells developed in the PhD thesis of Rojek-Wöckner were reproduced and acted as a reference for further development. In a second step, the electrochemically active surface of the anode functional layer was raised. By reducing the sintering temperature, reduced coarsening of the microstructure resulted during processing. However, this was found to be detrimental due to undesired side effects. At low anode thicknesses, mechanical stability of the layered composite anode suffered because of low sintering between the particles. In addition, at high anode functional layer thicknesses, gas permeability suffered because of a both thick and fine-pored layer. Availability of fuel gas in the layered composite anode decreased, leading to increased anode polarization resistance. By increasing the layer thickness, a positive side effect appeared by lowering the surface roughness. A low surface roughness is a requirement for a gas-tight PVD-thin film electrolyte. Therefore, this concept with a thicker anode functional layer was used to successfully implement a cell design with a 2 μm thick PVD-electrolyte. This can be taken as starting point for future improvement of a 2 μm thin-film electrolyte. By increasing the sintering temperature of the functional layer in this design as well, stability and permeability of the layered composite anode were increased. Still, signs of gas diffusion limitation at high current densities became visible. To overcome this, a further improved cell design was implemented. An electrochemically inactive Ni/YSZ-interlayer was exchanged by an electrochemically active Ni/GDC-layer. Compared to the reference cell concept of Rojek-Wöckner, the improved cell design with a double-layered Ni/GDC-anode functional layer enabled a performance increase from 1,29 A/cm$^{2}$ to 1,79 A/cm$^{2}$ and therefore by 38%. The active surface and the permeability of the layered composite anode were increased. Moreover, mechanical stability and reproducibility were enhanced. Furthermore, the cell showed lower deflection after processing easing the handling of the cell during next processing steps like stack assembling [...]

Note: Dissertation, Diss. Bochum, 2019

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Contributing Institute(s):

1. Werkstoffsynthese und Herstellungsverfahren (IEK-1)

Research Program(s):

1. 135 - Fuel Cells (POF3-135) (POF3-135)
2. SOFC - Solid Oxide Fuel Cell (SOFC-20140602) (SOFC-20140602)

Appears in the scientific report 2020

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